This invention relates to trihydrocarbyl silyl-substituted alkyl diaryl phosphate transition metal complex carbonylation catalysis.
More particularly, the subject of this invention is homogeneous, selective, low pressure alpha-olefin hydroformylation with tris-(silylalkyl diaryl phosphine) rhodium carbonyl hydride complex catalysts in the presence of excess phosphine ligand.
One aspect of the invention is the derivation of the silylalkyl diphenyl phosphine ligands via the anti-Markovnikov addition of a diaryl phosphine to the appropriate alkenyl silane.
Another aspect is concerned with the preparation of the transition metal complexes of these ligands via displacement reactions. Syntheses starting with tris-(triphenyl phosphine) rhodium carbonyl hydride and dicarbonyl acetylacetonato rhodium are specifically described.
A special aspect of the invention is concerned with the physicochemical and catalytic properties of the novel complexes, i.e., phosphine basicity and stereochemistry versus complex formation, equilibria and stability. The selectivity and rate of hydroformylation are correlated with temperature, concentration of excess ligand, carbon monoxide partial pressure and the presence of aldolization catalyst.
Finally, a special concern of the present invention is a continuous low pressure hydroformylation of alpha-olefins, particularly butane-1, propylene and pentenes at elevated temperatures. An exemplary feature of such hydroformylation involves a continuous product flashoff operation. In this process, gaseous reactants are continuously introduced into, and a mixture of gaseous products and unreacted feed is continuously removed from, the solution of the present homogeneous catalyst complex.
The main objective of the present invention is to provide selective silyl substituted alkyl diphenyl phosphine rhodium carbonyl hydride catalysts which are more stable, and can be used in an improved hydroformylation process at higher temperatures, than the widely used triaryl phosphine rhodium carbonyl hydride catalysts.
Transition metal complexes of both triphenyl phosphine and trialkyl phosphines are widely studied catalysts employed in hydroformylation, hydrogenation, etc., reactions. The monograph of Juergen Falbe, "New Synthesis with Carbon monoxide," Springer Verlag, New York, 1970, deals with the use of these materials in reactions of carbon monoxide, particularly carbonylations. In the realm of rhodium catalyzed hydroformylations of alpha-olefins, catalyst systems of triaryl phosphine and other trivalent phosphorus compound rhodium complexes in the presence of excess phosphine ligand which exhibited improved selectivity to normal aldehydes (over iso aldehydes) are described by R. L. Pruett and J. A. Smith in U.S. Pat. No. 3,527,809. In that patent, it is stated as being essential that the phosphorus ligands be of weakly basic character possess a half neutralization potential value at least 425, preferably at least 500, smaller than that of N,N' diphenylguanidine. The .DELTA.HNP is only about 400 for simple alkyl diphenyl phosphines, which are too basic according to Pruett and Smith.
Morrell and Sherman in German Offenlegungschrift No. 2,802,922 disclose unsubstituted alkyl diphenyl phosphines as components of stabilized tris-(triphenyl phosphine) rhodium carbonyl hydride plus excess triphenyl phosphine catalyst systems for hydroformylation of alpha-olefins with CO/H.sub.2 to give aldehydes.
In the area of silyl substituted alkyl phosphine transition metal complexes, the work of Grish Chandra is of importance. British Pat. Nos. 1,419,769; 1,420,982; 1,421,136 by Chandra disclose rhodium complexes of silyl alkyl phosphines, in each of which the rhodium had attached to it a halogen. These materials are disclosed as being useful for hydro-silylation, hydrogenation and hydroformylation. Specific examples are given only for the preparation of silylmethyl phosphine complexes and their use in hydrosilylation.
British Pat. Nos. 1,412,257; 1,414,662 and U.S. Pat. No. 3,856,837 (all to Chandra) describe nickel, palladium and platinum complexes of silylalkyl phosphines and their use of hydrosilylation, hydrogenation, and polymerization. In these patents, the transition metal has attached to it a halogen or --SCN group or --SZ wherein Z represents an alkyl radical having less than 18 carbon atoms or the phenyl radical.
In G.B. Pat. No. 1,412,257 the material is identified as a bridged binuclear complex.
In G.B. Pat. No. 1,414,662 the nickel, palladium or platinum transition group metal may have associated with it a hydrogen atom or other anionic liquid (X) which may be for example, H, Cl, Br, I, --NO.sub.2, --NO.sub.3, --SCN, --OCOCH.sub.3, an alkyl, aryl, alkaryl or aralkyl radical. However, materials wherein X is Br are the only ones actually prepared.
In U.S. Pat. No. 3,856,837, the nickel, palladium or platinum also have only halogens associated with them as anionic ligands (X).
G.B. Pat. No. 925,721 to H. Niebergall deals broadly with the addition of secondary phosphines to unsaturated silanes to provide silylhydrocarbyl phosphines. He discloses materials of the formula: ##STR1## wherein R.sub.1 and R.sub.2 are alkyl, cycloalkyl, aryl, alkaryl, aralkyl; R.sub.3 and R.sub.4 are alkyl, cycloalkyl, aryl, alkaryl, aralkyl or hydrogen; A is a halo, alkoxy, hydroxy, alkyl, alkaryl, cycloalkyl, aryl or aralkyl radical; Z is a hydrocarbon residue having from 1 to 10 carbon atoms and is preferably a saturated straight or branched chain hydrocarbon residue (or Z is a silicon to carbon linkage). If phosphorous is pentavalent, y is oxygen or sulfur; if phosphorous is trivalent, y is no substituent; n is 0 to 3. This patent contains no teaching that these materials can be complexed with transition metals to yield homogeneous catalysts useful in hydroformylation reactions.
Owen and Cooper disclose the preparation of similar compounds via displacement reactions of chlorophosphines and silylalkyl Grignard compounds or sodium phosphides and silylalkyl halides in British Pat. No. 1,179,242.
To obtain the vinyl triphenyl silane intermediate, vinyl trichloro silane was reacted with phenyl magnesium bromide in an ether-THF solvent mixture.
U.S. Pat. No. 3,067,227 to Fekete describes the preparation of alkoxysilylalkylphosphines via the method of reacting alkoxy silanes and unsaturated phosphines.
G.B. Pat. No. 1,182,763 to Jacques and Owen also disclose silylhydrocarbylphosphine intermediates useful in the preparation of the complexes of the present invention.
U.S. Pat. No. 3,726,809 and 3,832,404 to Allum et al. disclose heterogeneous hydroformylation catalysts (and processes using these catalysts). These heterogeneous catalysts are silylhydrocarbyl phosphine transition metal complexes, bonded to a support by the interaction of a reactive group on the silicon with at least one reactive hydroxyl group on the support which may also be silicon. See also U.S. Pat. Nos. 3,907,852 and 4,083,803 to Oswald and Murrell.